A366780 Number of distinct prime divisors of A000073(n) (tribonacci numbers).
0, 0, 1, 1, 1, 1, 2, 2, 1, 1, 2, 3, 2, 3, 2, 3, 1, 3, 4, 3, 3, 2, 2, 2, 3, 3, 3, 5, 3, 4, 5, 3, 4, 3, 5, 4, 5, 3, 5, 3, 2, 4, 2, 4, 5, 4, 4, 6, 2, 5, 5, 6, 3, 5, 7, 5, 2, 3, 5, 4, 6, 5, 4, 7, 3, 2, 4, 4, 3, 3, 4, 5, 2, 6, 6, 6, 5, 3, 6, 5, 4, 2, 6, 3, 6, 1, 7
Offset: 2
Keywords
Examples
a(8)=2 because the 8th tribonacci number 24 = 2^3*3 has 2 distinct prime factors.
Links
- Amiram Eldar, Table of n, a(n) for n = 2..365
Programs
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Mathematica
PrimeNu[LinearRecurrence[{1, 1, 1}, {1, 1, 2}, 87]] (* Amiram Eldar, Oct 23 2023 *)